With the exception of South Carolina, turnout among GOP voters has been tepid. Hordes of commentators, me included, have argued at length that this apathetic grumpiness reflects a deep dissatisfaction with the Republican field.

Worse, many Republicans recognize that their cantankerousness over their choices makes things worse. It’s a vicious cycle. As George Orwell once wrote: “A man may take to drink because he feels himself to be a failure, and then fail all the more completely because he drinks.” A bad candidate can win with enthusiastic voters and a good candidate can lose with unenthusiastic ones. But a bad candidate with unenthusiastic voters is like a submarine with screen doors: a guaranteed wreck.

Without minimizing the plight of the Republicans, there may be a glimmer of hope in a single overlooked fact: Democrats may have the same problem.

Generally speaking, Americans of all political stripes hate politics and politicians right now. Republicans are merely the focus of everyone’s attention because that’s where the action is. Everyone knows who the Democratic nominee will be. This gives Barack Obama all sorts of advantages. He can seem presidential and above the fray, he can raise money for the general election without getting bloodied by a primary challenger, and he can spend his time and resources unifying his party.

“When it comes to enthusiasm, my hunch is that more people will be excited to vote against Obama than to vote for him.” – Jonah Goldberg

But unity and enthusiasm are not the same thing. Everyone in the family can agree to eat Aunt Sally’s leftover casserole, but that doesn’t mean they’re going to be excited about it.

Obama won 2008 thanks to almost unprecedented voter enthusiasm, particularly among two key constituencies: young voters and black voters.

Take the youth vote. The whippersnappers cost John McCain the election. Obama won young voters by a two-to-one margin. If the voting age were 35, McCain would have won. Youth support was also a crucial source of energy for the Obama campaign, fueling all of the social-media buzz and burnishing Obama’s image as a change candidate in what was the mother of all change elections.

Almost four years later, the young people are less excited about Obama, and about politics in general.

Why? Because the “Great Recession” under Obama has been disproportionately brutal for younger workers. Last summer was the worst job market for young people since 1948. In 2010, the unemployment rate for college graduates 24 and younger hit an all-time high.

The youth unemployment rate is improving, but the mood of young people isn’t where Obama needs it. A recent Harvard survey found that a majority of 18- to 29-year-old voters believe the country is going in the wrong direction, and a plurality of young Americans believe Obama will lose.

For black Americans, the economy has been much worse. The unemployment rate for blacks is twice that of whites. While Obama’s support among black voters remains in the stratosphere, the relevant issue isn’t the approval rate in polls but the turnout rate in November, particularly in a string of crucial swing states where Obama remains unpopular. Obama’s 2008 victories in the indispensible states of Pennsylvania, Ohio, and Florida were almost entirely attributable to massive increases in the number of black voters and young voters, as were his surprise wins in North Carolina and Virginia.

If young people don’t turn out in lopsided numbers, or if Obama once again receives 95 percent of the black vote but the black share of the overall vote goes down, Obama’s in grave trouble.

And it’s hard to imagine many people will be more excited for Obama in 2012 than they were in 2008 — a point even Obama concedes on the stump. It’s not just the sour economy either. Americans who were exhausted with George W. Bush were open to Obama’s rhetorical grandiosity in 2008. Now they know the man, and while they may still like him, far fewer people love him, which may help explain why Democrats are raising less money in 2012 than they were at this time in 2008.

Consider Obama’s decision to endorse the very super PACs he not long ago denounced as a threat to democracy. GOP-aligned groups have been raising enormous sums. In January, a pro-Romney group called Restore Our Future raised $6.6 million. The pro-Newt Gingrich group Winning Our Future raised $11 million.

Over the same period, the pro-Obama Priorities USA raised $59,000.

Things are ugly for Republicans right now. But that might just be because things are ugly all over. And when it comes to enthusiasm, my hunch is that more people will be excited to vote against Obama than to vote for him.